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T Boucher

Publications and source records attributed to T Boucher.

7 recordsLinked to original sources
PubMed1984

Inhibition of semicarbazide-sensitive amine oxidase by monoamine oxidase B inhibitors from the oxazolidinone series.

The purpose of the present work was to study the semicarbazide-sensitive amine oxidase (SSAO) inhibitory properties of MD 240931 and MD 240928 (the two enantiomers of MD 780236) as well as those of the corresponding primary amines, MD220662 and MD220661, in rat heart and aorta. MD240928 and MD240931 are rather weak SSAO inhibitors, MD 240931 being more potent than MD 240928. Of the four compounds studied, the most potent inhibitor of SSAO is MD 220662, its IC50 value ranging from 2.10(-6) to 6.10(-6)M. The SSAO inhibitory potency of this compound does not change significantly with the time of preincubation in both the absence and presence of clorgyline (10(-4)M). MD 220661 is also an inhibitor of SSAO; however, its SSAO inhibitory potency, which without preincubation is comparable to that of MD 220662, does decrease with the time of preincubation to the same extent in both the absence and presence of clorgyline (10(-4)M). These results suggest that MD 220661 is not only an inhibitor of SSAO, but is also a substrate of the enzyme.

Animals↗
PubMed1983

Intestinal metabolism of tyramine by both forms of monoamine oxidase in the rat.

The two forms of monoamine oxidase (MAO) in rat intestine and brain homogenates were found to have different Km and Vmax values towards tyramine. The Km values for the A-form of the enzyme towards this substrate were around 120 microM in both cases, whereas the values for the B-form were about 240 microM. As a consequence, the ratio of activities (MAO-A: MAO-B) towards tyramine are dependent upon the substrate concentration. The MAO-A-selective inhibitors, toloxatone and cimoxatone, were found to be competitive inhibitors of the oxidation of tyramine by the A-form of this enzyme in the rat intestine, with Ki values of 3.4 microM and 3.7 nM respectively. The significance of these results in relation to the "cheese effect", a pressor response to tyramine after monoamine oxidase inhibition, are discussed.

Animals↗
PubMed1983

The deamination of noradrenaline and 5-hydroxytryptamine by rat brain and heart monoamine oxidase and their inhibition by cimoxatone, toloxatone and MD 770222.

In both rat brain and heart, noradrenaline and 5-hydroxytryptamine are metabolised predominantly by monoamine oxidase-A. The Km values for 14C-noradrenaline in the rat brain and heart are 290 microM and 300 microM, respectively, whereas for 14C-5-hydroxytryptamine the values are 180 microM and 140 microM, respectively. In the rat brain, mixed substrate experiments suggested that 14C-noradrenaline and 14C-5-hydroxytryptamine are metabolised at the same active centre. Both substrates are inhibited with similar Ki values by the reversible inhibitors cimoxatone, toloxatone and MD 770222.

Animals↗